Polarizing plate and image display device

Abstract

To provide a polarizing plate that can be suitably used for bendable or foldable image display devices, and to provide an image display device.SOLUTION: A polarizing plate according to an embodiment of the present invention comprises a polarizer and a protective layer. The protective layer is provided at least on one surface of the polarizer. The number of times of bending endurance of the protective layer in an MIT test is 200 or more.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a polarizing plate and an image display device. [Background technology]

[0002] Image display devices, such as liquid crystal display devices and electroluminescence (EL) display devices (e.g., organic EL display devices and inorganic EL display devices), are rapidly becoming widespread. Image display devices typically use a polarizing plate that includes a polarizer and a protective layer (see, for example, Patent Document 1). In recent years, applications of image display devices have become more diverse, and efforts are being made to make image display devices flexible and bendable. However, when the polarizing plate described in Patent Document 1 is applied to a bendable or foldable image display device, the bendability of the image display device may become insufficient. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2022-153440 A Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention has been made to solve the above-mentioned problems in the conventional art, and a main object of the present invention is to provide a polarizing plate and an image display device that can be suitably applied to a bendable or foldable image display device. [Means for solving the problem]

[0005] [1] A polarizing plate according to one embodiment of the present invention includes a polarizer and a protective layer. The protective layer is disposed on at least one side of the polarizer. The number of flexions of the protective layer in an MIT test is 200 or more. [2] An image display device according to another aspect of the present invention includes the polarizing plate according to the above item [1] and a bendable image display panel, in this order. [3] In the image display device according to the above [2], a thickness ratio of the protective layer to a thickness of the image display panel may be 1-2. Effect of the Invention

[0006] According to the embodiments of the present invention, it is possible to realize a polarizing plate and an image display device that can be suitably applied to a bendable or foldable image display device. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic cross-sectional view of a polarizing plate according to one embodiment of the present invention. [Diagram 2] FIG. 2 is a schematic cross-sectional view of a polarizing plate according to another embodiment of the present invention. [Diagram 3] FIG. 3 is a schematic cross-sectional view of an image display device including the polarizing plate of FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Representative embodiments of the present invention will be described below, but the present invention is not limited to these embodiments. In addition, in order to clarify the description, the width, thickness, shape, etc. of each part may be shown in a schematic manner compared to the embodiment, but these are merely examples and do not limit the interpretation of the present invention.

[0009] (Definition of terms and symbols) The definitions of terms and symbols used in this specification are as follows. (1) Refractive index (nx, ny, nz) "nx" is the refractive index in the direction in which the in-plane refractive index is maximum (i.e., the slow axis direction), "ny" is the refractive index in the direction perpendicular to the slow axis in the plane (i.e., the fast axis direction), and "nz" is the refractive index in the thickness direction. (2) In-plane phase difference (Re) "Re(λ)" is the in-plane retardation measured with light of wavelength λ nm at 23° C. For example, "Re(550)" is the in-plane retardation measured with light of wavelength 550 nm at 23° C. Re(λ) is calculated by the formula: Re(λ)=(nx-ny)×d, where d(nm) is the thickness of the layer (film). (3) Retardation in the thickness direction (Rth) "Rth(λ)" is the retardation in the thickness direction measured with light of wavelength λ nm at 23° C. For example, "Rth(550)" is the retardation in the thickness direction measured with light of wavelength 550 nm at 23° C. Rth(λ) is calculated by the formula: Rth(λ)=(nx-nz)×d, where d(nm) is the thickness of the layer (film).

[0010] A. Overall structure of polarizing plate FIG. 1 is a schematic cross-sectional view of a polarizing plate according to one embodiment of the present invention. As shown in FIG. 1, a polarizing plate 100 includes a polarizer 2 and a protective layer 1. The protective layer 1 is disposed on at least one side of the polarizer 2. The protective layer 1 typically has flexibility. The number of flexions of the protective layer 1 in an MIT test (hereinafter, referred to as the MIT flexion number) is 200 or more. The MIT test can be performed in accordance with, for example, JIS P 8115. When the MIT bending number of the protective layer is 200 or more, sufficient bending durability can be imparted to a polarizing plate including the protective layer and the polarizer. Such a polarizing plate is applicable to a bendable image display device (e.g., a liquid crystal display device, an organic EL display device, an inorganic EL display device), preferably a foldable image display device, more preferably a foldable organic EL display device.

[0011] The MIT flexion number of the protective layer 1 is preferably at least 500, more preferably at least 800, and even more preferably at least 1000. When the MIT flexion number of the protective layer is equal to or greater than such a lower limit, the flexion durability of the polarizing plate can be further improved. On the other hand, the MIT flexion number of the protective layer 1 is, for example, 6000 times or less, preferably 3000 times or less, and more preferably 2000 times or less.

[0012] The indentation modulus of the protective layer 1 is, for example, 3.00 GPa or more, preferably 3.10 GPa or more, and more preferably 3.20 GPa or more. When the indentation modulus of the protective layer is equal to or more than such a lower limit, the bending durability of the polarizing plate can be further improved. On the other hand, the indentation modulus of the protective layer 1 is, for example, 7.00 GPa or less, preferably 6.00 GPa or less, more preferably 4.00 GPa or less, and even more preferably 3.50 GPa or less. If the indentation modulus of the protective layer is equal to or less than such an upper limit, cracking of the protective layer during bending can be suppressed. The indentation modulus can be measured, for example, in accordance with JIS Z 2255.

[0013] The breaking elongation of the protective layer 1 at 25° C. is, for example, 20 mm or more, preferably 25 mm or more, and more preferably 30 mm or more. When the breaking elongation of the protective layer is equal to or more than such a lower limit, the bending durability of the polarizing plate can be further improved. On the other hand, the breaking elongation of the protective layer 1 is, for example, 150 mm or less, preferably 130 mm or less, more preferably 100 mm or less, and even more preferably 50 mm or less. If the breaking elongation of the protective layer is not more than such an upper limit, deformation of the protective layer can be suppressed. The breaking elongation can be measured, for example, in accordance with JIS K 7127.

[0014] The loss tangent tanδ of the protective layer 1 at 85°C and 85% RH (relative humidity) is, for example, 15×10 -2 Less than or equal to 13 x 10 -2 Less than or equal to 10×10 -2 Less than 7.0×10, more preferably -2 On the other hand, the lower limit of the loss tangent tan δ of the protective layer 1 at 85° C. and 85% RH (relative humidity) is typically 4.0×10 -2 It is. The loss tangent tanδ of the protective layer 1 at 100° C. is, for example, 15×10 -2 Less than or equal to 13 x 10 -2Less than or equal to 10×10 -2 Less than 8.0×10, more preferably -2 The following is particularly preferably 6.0×10 -2 On the other hand, the lower limit of the loss tangent tan δ of the protective layer 1 at 100° C. is typically 3.0×10 -2 The tan δ of the protective layer is observed, for example, by measuring the dynamic viscoelasticity in a tensile mode at a measurement frequency of 5 Hz. If the tan δ of the protective layer is equal to or higher than the lower limit, stress relaxation during bending can be achieved, and failure modes such as cracks due to residual stress, etc. If the tan δ of the protective layer is equal to or lower than the upper limit, no creases are formed even when the display is bent multiple times, and good image display can be maintained.

[0015] The thickness of the protective layer 1 is, for example, 10 μm or more, preferably 20 μm or more. If the thickness of the protective layer is equal to or more than such a lower limit, excellent bending durability can be stably imparted to the polarizing plate. On the other hand, the thickness of the protective layer 1 is, for example, 130 μm or less, preferably 100 μm or less, more preferably 80 μm or less, even more preferably 55 μm or less, particularly preferably 47 μm or less, particularly preferably 42 μm or less, and most preferably 30 μm or less. If the thickness of the protective layer is equal to or less than such an upper limit, excellent bending durability can be stably imparted to the polarizing plate, and the polarizing plate can be made thinner.

[0016] 2, in one embodiment, the protective layer 1 is disposed on both sides of the polarizer 2. Hereinafter, the protective layer 1 disposed on one side of the polarizer 2 may be referred to as a first protective layer 1a, and the protective layer 1 disposed on the other side of the polarizer 2 may be referred to as a second protective layer 1b to distinguish them from each other.

[0017] The components of the polarizing plate will be described in detail below.

[0018] B. Polarizer Any appropriate polarizer may be adopted as the polarizer 2. For example, the resin film forming the polarizer may be composed of a single-layer resin film, or may be prepared using a laminate of two or more layers.

[0019] Specific examples of polarizers made of a single-layer resin film include hydrophilic polymer films such as polyvinyl alcohol (PVA) films, partially formalized PVA films, and partially saponified ethylene-vinyl acetate copolymer films that have been dyed with a dichroic substance such as iodine or a dichroic dye and stretched, and polyene-based oriented films such as dehydrated PVA films and dehydrochlorinated polyvinyl chloride films. A polarizer obtained by dyeing a PVA film with iodine and uniaxially stretching it is preferable because of its excellent optical properties.

[0020] Specific examples of polarizers obtained using a laminate include a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer formed by coating on the resin substrate. A polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer formed by coating on the resin substrate can be produced by, for example, applying a PVA-based resin solution to the resin substrate and drying the resin substrate to form a PVA-based resin layer on the resin substrate to obtain a laminate of the resin substrate and the PVA-based resin layer; stretching and dyeing the laminate to make the PVA-based resin layer into a polarizer. In one embodiment of the present invention, a polyvinyl alcohol-based resin layer containing a halide and a polyvinyl alcohol-based resin is preferably formed on one side of the resin substrate. The stretching typically includes immersing the laminate in an aqueous boric acid solution to stretch it. Furthermore, the stretching may further include, as necessary, stretching the laminate in air at a high temperature (for example, 95° C. or higher) before stretching in the aqueous boric acid solution. In addition, in one embodiment of the present invention, the laminate is preferably subjected to a drying shrinkage treatment in which the laminate is heated while being transported in the longitudinal direction to shrink the laminate by 2% or more in the width direction. Typically, the manufacturing method of this embodiment includes subjecting the laminate to an air-assisted stretching treatment, a dyeing treatment, an underwater stretching treatment, and a drying shrinkage treatment in this order. By introducing the auxiliary stretching, even when PVA is applied onto a thermoplastic resin, it is possible to increase the crystallinity of PVA, and to achieve high optical properties. At the same time, by increasing the orientation of PVA in advance, problems such as a decrease in the orientation of PVA or dissolution when immersed in water in the subsequent dyeing step or stretching step can be prevented, and high optical properties can be achieved. Furthermore, when the PVA-based resin layer is immersed in a liquid, the disorder of the orientation of polyvinyl alcohol molecules and the decrease in the orientation can be suppressed compared to when the PVA-based resin layer does not contain a halide. This can improve the optical properties of a polarizer obtained through a treatment step in which the laminate is immersed in a liquid, such as a dyeing treatment and an underwater stretching treatment. Furthermore, the optical properties can be improved by shrinking the laminate in the width direction through drying shrinkage treatment.The obtained laminate of resin substrate / polarizer may be used as it is (i.e., the resin substrate may be used as a protective layer for the polarizer), or the resin substrate may be peeled off from the laminate of resin substrate / polarizer, and any suitable protective layer may be laminated on the peeled surface depending on the purpose. Details of the method for producing such a polarizer are described in, for example, JP2012-73580A and JP6470455A. The entire disclosures of these publications are incorporated herein by reference.

[0021] The dyeing with iodine is carried out, for example, by immersing the PVA-based film in an aqueous iodine solution. The stretching ratio of the uniaxial stretching is preferably 3 to 7 times. The stretching may be carried out after the dyeing treatment, or may be carried out while dyeing. Alternatively, the film may be stretched and then dyed. If necessary, the PVA-based film may be subjected to a swelling treatment, a crosslinking treatment, a washing treatment, a drying treatment, or the like. For example, by immersing the PVA-based film in water and washing it with water before dyeing, it is possible to wash off dirt and antiblocking agents on the surface of the PVA-based film, and also to swell the PVA-based film and prevent uneven dyeing.

[0022] The thickness of the polarizer 2 is, for example, 1 μm to 80 μm, preferably 1 μm to 15 μm, more preferably 1 μm to 12 μm, and further preferably 3 μm to 12 μm. When the thickness of the polarizer is within this range, curling during heating can be well suppressed and good appearance durability during heating can be obtained.

[0023] The polarizer 2 typically exhibits absorption dichroism at any wavelength of 380 nm to 780 nm. The single transmittance of the polarizer 2 is, for example, 41.5% to 46.0%, preferably 43.0% to 46.0%, and more preferably 44.5% to 46.0%. The degree of polarization of the polarizer 2 is preferably 97.0% or more, more preferably 99.0% or more, and even more preferably 99.9% or more.

[0024] C. Protective layer The protective layer 1 is composed of a resin film containing a resin material as a main component. Specific examples of the resin material include transparent resins such as cycloolefin (COP) resins such as polynorbornene resins, polyester resins such as polyethylene terephthalate (PET) resins, cellulose resins such as triacetyl cellulose (TAC), polycarbonate (PC) resins, (meth)acrylic resins, polyvinyl alcohol resins, polyamide resins, polyimide resins, polyethersulfone resins, polysulfone resins, polystyrene resins, polyolefin resins, and acetate resins. In addition, thermosetting resins or ultraviolet curing resins such as (meth)acrylic resins, urethane resins, (meth)acrylic urethane resins, epoxy resins, and silicone resins are also included. The term "(meth)acrylic resin" refers to acrylic resins and / or methacrylic resins. In addition, glassy polymers such as siloxane polymers are also included. In addition, the polymer films described in JP 2001-343529 A (WO01 / 37007) can also be used. The material of this film may be, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in the side chain, and a thermoplastic resin having a substituted or unsubstituted phenyl group and a nitrile group in the side chain, such as a resin composition having an alternating copolymer of isobutene and N-methylmaleimide, and an acrylonitrile-styrene copolymer. The polymer film may be, for example, an extrusion product of the above resin composition. The materials of the resin film may be used alone or in combination.

[0025] Of these resin materials, preferably, PC-based resins are used.

[0026] The PC resin contains at least a structural unit derived from a dihydroxy compound having a bond structure represented by the following structural formula (1), and has at least one bond structure -CH 2PC resins are produced by reacting a dihydroxy compound containing at least a dihydroxy compound having -O- with a carbonic acid diester in the presence of a polymerization catalyst. In other words, PC resins contain structural units derived from the dihydroxy compound and carbonate groups derived from the carbonic acid diester. [ka]

[0027] Here, the dihydroxy compound having the bond structure represented by structural formula (1) is a compound having two alcoholic hydroxyl groups and a linking group -CH 2 Any compound having any structure can be used as long as it contains a structure having --O-- and can react with a carbonate diester in the presence of a polymerization catalyst to produce a polycarbonate, and two or more types of compounds may be used in combination.

[0028] In addition, a dihydroxy compound not having the bond structure represented by the above structural formula (1) may be used in combination as a dihydroxy compound for use in a PC resin. Hereinafter, a dihydroxy compound having the bond structure represented by structural formula (1) may be abbreviated as dihydroxy compound (A), and a dihydroxy compound not having the bond structure represented by structural formula (1) may be abbreviated as dihydroxy compound (B).

[0029] (Dihydroxy compound (A)) The linking group -CH in the dihydroxy compound (A) 2 "-O-" means a structure in which the linking group is bonded to an atom other than a hydrogen atom to form a molecule. In this linking group, the atom to which at least an oxygen atom can be bonded or the atom to which both a carbon atom and an oxygen atom can be bonded at the same time is preferably a carbon atom. 2 The number of "-O-" is preferably 1 or more, and more preferably 2 to 4.

[0030] Specific examples of the dihydroxy compound (A) include 9,9-bis(4-(2-hydroxyethoxy)phenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-methylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-isopropylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-isobutylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-tert-butylphenyl)fluorene, and 9,9-bis(4-(2-hydroxyethoxy)-3-tert-butylphenyl)fluorene. )-3-cyclohexylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-phenylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3,5-dimethylphenyl)fluorene, 9,9-bis(4-(2-hydroxyethoxy)-3-tert-butyl-6-methylphenyl)fluorene, and 9,9-bis(4-(3-hydroxy-2,2-dimethylpropoxy)phenyl)fluorene;Bis[4-(2-hydroxyethoxy)phenyl]methane, bis[4-(2-hydroxyethoxy)phenyl]diphenylmethane, 1,1-bis[4-(2-hydroxyethoxy)phenyl]ethane, 1,1-bis[4-(2-hydroxyethoxy)phenyl]-1-phenylethane, 2,2-bis[4-(2-hydroxyethoxy)phenyl]propane, 2,2-bis[4-(2-hydroxyethoxy)-3-methylphenyl]propane, 2,2-bis[3,5-dimethyl-4-(2-hydroxyethoxy)phenyl] 1,1-bis[4-(2-hydroxyethoxy)phenyl]propane, 1,1-bis[4-(2-hydroxyethoxy)phenyl]-3,3,5-trimethylcyclohexane, 1,1-bis[4-(2-hydroxyethoxy)phenyl]cyclohexane, 1,4-bis[4-(2-hydroxyethoxy)phenyl]cyclohexane, 1,3-bis[4-(2-hydroxyethoxy)phenyl]cyclohexane, 2,2-bis[4-(2-hydroxyethoxy)-3-phenylphenyl]propane, 2,2-bis[(2-hydroxyethoxy)-3-phenylphenyl]propane, isopropylphenyl]propane, 2,2-bis[3-tert-butyl-4-(2-hydroxyethoxy)phenyl]propane, 2,2-bis[4-(2-hydroxyethoxy)phenyl]butane, 2,2-bis[4-(2-hydroxyethoxy)phenyl]-4-methylpentane, 2,2-bis[4-(2-hydroxyethoxy)phenyl]octane, 1,1-bis[4-(2-hydroxyethoxy)phenyl]decane, 2,2-bis[3-bromo-4-(2-hydroxyethoxy)phenyl]propane bis(hydroxyalkoxyaryl)alkanes, such as 2,2-bis[3-cyclohexyl-4-(2-hydroxyethoxy)phenyl]propane; bis(hydroxyalkoxyaryl)cycloalkanes, such as 1,1-bis[4-(2-hydroxyethoxy)phenyl]cyclohexane, 1,1-bis[3-cyclohexyl-4-(2-hydroxyethoxy)phenyl]cyclohexane, and 1,1-bis[4-(2-hydroxyethoxy)phenyl]cyclopentane;Dihydroxyalkoxy diaryl ethers, such as 4,4'-bis(2-hydroxyethoxy)diphenyl ether and 4,4'-bis(2-hydroxyethoxy)-3,3'-dimethyldiphenyl ether; bishydroxyalkoxy aryl sulfides, such as 4,4'-bis(2-hydroxyethoxyphenyl) sulfide and 4,4'-bis[4-(2-dihydroxyethoxy)-3-methylphenyl] sulfide; bishydroxyalkoxy aryl sulfoxides, such as 4,4'-bis(2-hydroxyethoxyphenyl) sulfone and 4,4'-bis[4-(2- bishydroxyalkoxyarylsulfones, such as 1,4-bishydroxyethoxybenzene, bishydroxyalkoxybenzenes, such as 1,3-bis[2-[4-(2-hydroxyethoxy)phenyl]propyl]benzene, 1,4-bis[2-[4-(2-hydroxyethoxy)phenyl]propyl]benzene, 4,4'-bis(2-hydroxyethoxy)biphenyl, 1,3-bis[4-(2-hydroxyethoxy)phenyl]-5,7-dimethyladamantane, anhydrous sugar alcohols, such as dihydroxy compounds represented by the following formula (2), and compounds having a cyclic ether structure, such as spiro glycols, such as those represented by the following general formula (3). The dihydroxy compounds (A) may be used alone or in combination.

[0031] [ka]

[0032] [ka]

[0033] Of these dihydroxy compounds (A), preferred is the dihydroxy compound represented by the above formula (2). Examples of the dihydroxy compound represented by the above formula (2) include isosorbide, isomannide, and isoidite, which are stereoisomeric, and these may be used alone or in combination of two or more. Among the dihydroxy compounds (A), isosorbide obtained by dehydration condensation of sorbitol produced from various starches, which are abundant and easily available as resources, is most preferred in terms of availability, ease of production, optical properties, and moldability.

[0034] The ratio of the structural units derived from the dihydroxy compound (A) to the total structural units derived from the dihydroxy compounds contained in the PC resin is, for example, 10 mol% or more, preferably 40 mol% or more, more preferably 60 mol% or more. On the other hand, the ratio of the structural units derived from the dihydroxy compound (A) is, for example, 100 mol% or less, preferably 90 mol% or less, more preferably 80 mol% or less, and even more preferably 70 mol% or less. When the ratio of the dihydroxy compound (A) is within the above range, the MIT bending number of the protective layer can be stably adjusted to the above range.

[0035] (Dihydroxy Compound (B)) As the dihydroxy compound that is the structural unit of the PC resin, dihydroxy compound (A) and dihydroxy compound (B) can be used together. By using dihydroxy compounds (A) and (B) in combination, the MIT bending number of the protective layer can be more stably adjusted to the above range.

[0036] The dihydroxy compound (B) is typically a dihydroxy compound other than the dihydroxy compound (A). Examples of the dihydroxy compound (B) include alicyclic dihydroxy compounds, aliphatic dihydroxy compounds, oxyalkylene glycols, aromatic dihydroxy compounds, and diols having a cyclic ether structure. The dihydroxy compounds (B) may be used alone or in combination. Of the dihydroxy compounds (B), preferably, alicyclic dihydroxy compounds are used.

[0037] The alicyclic dihydroxy compound is not particularly limited, but preferably includes a compound having a 5-membered ring structure or a 6-membered ring structure. The 6-membered ring structure may be fixed to a chair or boat shape by a covalent bond. When the alicyclic dihydroxy compound has a 5-membered ring or a 6-membered ring structure, the heat resistance of the resulting PC resin can be improved. The number of carbon atoms contained in the alicyclic dihydroxy compound is, for example, 70 or less, preferably 50 or less, more preferably 30 or less.

[0038] Specific examples of the alicyclic dihydroxy compound containing a 5-membered ring structure or a 6-membered ring structure include alicyclic dihydroxy compounds represented by the following general formula (I) or (II). HOCH 2 -R 1 -CH 2 OH (I) H.O.R. 2 -OH (II) (In formulas (I) and (II), R 1 and R 2 Each of represents a cycloalkylene group having 4 to 20 carbon atoms.

[0039] Cyclohexanedimethanol, which is an alicyclic dihydroxy compound represented by the above general formula (I), is 1 is represented by the following general formula (Ia) (wherein R 3 represents an alkyl group having 1 to 12 carbon atoms or a hydrogen atom. Specific examples of such isomers include 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, and 1,4-cyclohexanedimethanol.

[0040] [ka]

[0041] The alicyclic dihydroxy compound represented by the above general formula (I), tricyclodecane dimethanol or pentacyclopentadecanedimethanol, is represented by the general formula (I), 1 is represented by the following general formula (Ib) (wherein n is 0 or 1):

[0042] [ka]

[0043] Decalin dimethanol or tricyclotetradecane dimethanol, which is an alicyclic dihydroxy compound represented by the above general formula (I), is a compound represented by the general formula (I) 1 is represented by the following general formula (Ic) (wherein m is 0 or 1). Specific examples of such isomers include 2,6-decalin dimethanol, 1,5-decalin dimethanol, and 2,3-decalin dimethanol.

[0044] [ka]

[0045] Norbornane dimethanol, which is an alicyclic dihydroxy compound represented by the above general formula (I), is 1 The isomers include various isomers represented by the following general formula (Id): Specific examples of such isomers include 2,3-norbornane dimethanol and 2,5-norbornane dimethanol.

[0046] [ka]

[0047] Adamantane dimethanol, which is an alicyclic dihydroxy compound represented by general formula (I), is 1The isomers include various isomers represented by the following general formula (Ie): A specific example of such isomers is 1,3-adamantanedimethanol.

[0048] [ka]

[0049] Cyclohexanediol, which is an alicyclic dihydroxy compound represented by the above general formula (II), is 2 is represented by the following general formula (IIa) (wherein R 3 represents an alkyl group having 1 to 12 carbon atoms or a hydrogen atom. Specific examples of such isomers include 1,2-cyclohexanediol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, and 2-methyl-1,4-cyclohexanediol.

[0050] [ka]

[0051] The alicyclic dihydroxy compound represented by the above general formula (II), tricyclodecanediol or pentacyclopentadecanediol, is a compound represented by the general formula (II), 2 is represented by the following general formula (IIb) (wherein n is 0 or 1):

[0052] [ka]

[0053] Decalindiol or tricyclotetradecanediol, which is an alicyclic dihydroxy compound represented by the above general formula (II), is a compound represented by the general formula (II) in which R 2is represented by the following general formula (IIc) (wherein m is 0 or 1). Specific examples of such isomers include 2,6-decalindiol, 1,5-decalindiol, and 2,3-decalindiol.

[0054] [ka]

[0055] Norbornanediol, which is an alicyclic dihydroxy compound represented by the above general formula (II), is 2 is represented by the following general formula (IId): Specific examples of such isomers include 2,3-norbornanediol and 2,5-norbornanediol.

[0056] [ka]

[0057] The adamantanediol, which is an alicyclic dihydroxy compound represented by the above general formula (II), is represented by the following general formula (II): 2 is represented by the following general formula (IIe): A specific example of such an isomer is 1,3-adamantanediol.

[0058] [ka]

[0059] Among the specific examples of the alicyclic dihydroxy compound described above, preferred are cyclohexanedimethanols, tricyclodecane dimethanols, adamantanediols, and pentacyclopentadecanedimethanols. From the viewpoints of availability and ease of handling, more preferred are 1,4-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,2-cyclohexanedimethanol, and tricyclodecane dimethanol, and even more preferred is tricyclodecane dimethanol.

[0060] The ratio of the structural units derived from the dihydroxy compound (B) to the total structural units derived from the dihydroxy compounds contained in the PC resin is, for example, 0 mol% or more, preferably 10 mol% or more, more preferably 20 mol% or more, and even more preferably 30 mol% or more. On the other hand, the ratio of the structural units derived from the dihydroxy compound (B) is, for example, 90 mol% or less, preferably 60 mol% or less, and more preferably 40 mol% or less.

[0061] Details of these PC resins are described, for example, in JP 2012-31370 A (Patent No. 5448264), the disclosure of which is incorporated herein by reference.

[0062] In one embodiment, the PC resin contains a structural unit derived from the dihydroxy compound (A) represented by the above formula (2), a structural unit derived from the alicyclic dihydroxy compound (B) represented by the above general formula (I), and a carbonate group linking them together. When a PC resin containing these structural units is applied to a resin film, the MIT bending number of the protective layer can be more stably adjusted to the above range. In such a PC resin, the molar ratio (A:B) of the structural unit derived from the dihydroxy compound (A) represented by the above formula (2) to the structural unit derived from the alicyclic dihydroxy compound (B) represented by the above general formula (I) is, for example, 5:5 to 9:1, and preferably 6:4 to 8:2. In such a PC resin, the combination of the dihydroxy compound (A) represented by the above formula (2) and the alicyclic dihydroxy compound (B) represented by the above general formula (I) is preferably a combination of isosorbide and tricyclodecane dimethanol.

[0063] The protective layer 1 may contain any appropriate additive in addition to the above-mentioned resin material. Examples of the additive include an antioxidant, an ultraviolet absorber, a light stabilizer, a nucleating agent, a filler, a pigment, a surfactant, and an antistatic agent. Any appropriate surface treatment layer may be provided on the surface of the protective layer 1 (the surface opposite to the polarizer 2). Examples of the surface treatment layer include a hard coat layer, an easy-adhesion layer, an easy-slip layer, an antiblocking layer, an antistatic layer, an antireflection layer, and an anti-oligomer layer.

[0064] The protective layer 1 typically has optical isotropy. In this specification, the term "optically isotropic" means that the in-plane retardation Re(550) and the retardation Rth(550) in the thickness direction are in the following ranges. The in-plane retardation Re(550) of the protective layer 1 is, for example, 10 nm or less, preferably 5 nm or less, and more preferably 3 nm or less. On the other hand, the lower limit of the in-plane retardation Re(550) of the protective layer 1 is typically 0 nm. The protective layer 1 has a thickness direction retardation Rth(550) of, for example, −10 nm to +10 nm, and preferably −5 nm to +5 nm.

[0065] The total light transmittance of the protective layer 1 is, for example, 80% or more, preferably 85% or more, more preferably 90% or more, and further preferably 95% or more. The haze value of the protective layer 1 is, for example, 2.0% or less, preferably 1.5% or less, more preferably 1.0% or less, even more preferably 0.7% or less, particularly preferably 0.5% or less, and particularly preferably 0.3% or less. The lower limit of the haze value of the protective layer 1 is typically 0.05%. When the total light transmittance and / or haze value of the protective layer is within such range, the protective layer can be prevented from affecting the optical properties of the polarizer.

[0066] D. Adhesive layer (adhesive layer or adhesive layer) Although not shown, the protective layer 1 is typically attached to the polarizer 2 via an adhesive layer (a pressure-sensitive adhesive layer or an adhesive layer).

[0067] Examples of the adhesive constituting the adhesive layer include (meth)acrylic adhesives, rubber adhesives, vinyl alkyl ether adhesives, silicone adhesives, polyester adhesives, polyamide adhesives, urethane adhesives, fluorine adhesives, epoxy adhesives, and polyether adhesives. The adhesives may be used alone or in combination of two or more. Of the adhesives, (meth)acrylic adhesives are preferred.

[0068] The thickness of the pressure-sensitive adhesive layer is typically 10 μm to 250 μm, and preferably 10 μm to 150 μm. The pressure-sensitive adhesive layer may be a single layer or may have a laminated structure.

[0069] The pressure-sensitive adhesive layer has a storage modulus (G') of, for example, 0.01 MPa to 1.00 MPa, and preferably 0.05 MPa to 0.50 MPa at 25° C. When the storage modulus of the pressure-sensitive adhesive layer is within such a range, a polarizing plate having very excellent flexibility can be realized, and as a result, a bendable or foldable image display device (particularly an organic EL display device) can be realized.

[0070] The adhesive constituting the adhesive layer may be, for example, a heat-curable adhesive or an active energy ray-curable adhesive, preferably an ultraviolet ray-curable adhesive. The thickness of the adhesive layer is, for example, 0.4 μm or more and 3.0 μm or less. Of these adhesive layers, the adhesive layer is preferable.

[0071] E. Image display device In one embodiment, the polarizing plate described in any one of the above items A to D is attached to a bendable image display panel. Fig. 3 is a schematic cross-sectional view of an image display device including the polarizing plate of Fig. 2. The image display device 200 in the illustrated example includes a polarizing plate 100 and a bendable image display panel 5 in this order.

[0072] The polarizing plate 100 is typically disposed on the viewing side of the image display panel 5. In one embodiment, the polarizing plate 100 is attached to the image display panel 5 via any appropriate adhesive layer (a pressure-sensitive adhesive layer or an adhesive layer). The bendable image display panel 5 typically includes an image display cell. Examples of the bendable image display panel 5 include a liquid crystal display panel, an organic EL panel, and an inorganic EL panel, and preferably an organic EL panel. The bendable image display panel 5 is described in, for example, JP 2017-126061 A. The entire disclosures of these publications are incorporated herein by reference. As the adhesive layer for attaching the polarizing plate 100 to the image display panel 5, preferably, the above-mentioned pressure-sensitive adhesive layer is used, and more preferably, a pressure-sensitive adhesive layer made of an acrylic pressure-sensitive adhesive is used.

[0073] In one embodiment, the thickness of the protective layer 1 included in the polarizing plate 100 is, for example, 0.6 to 2.2, and preferably 1.0 to 2.0, relative to the thickness of the image display panel 5. When the thickness ratio between the protective layer and the image display panel is within such a range, suitable flexibility can be stably imparted to the image display device.

[0074] As described above, such an image display device 200 is bendable or foldable. Note that the image display device may be referred to as an optical display device, the image display panel may be referred to as an optical display panel, and the image display cell may be referred to as an optical display cell. EXAMPLES

[0075] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. The methods for measuring the various properties are as follows.

[0076] (1) MIT bending times of the protective layer (resin film) In the examples and comparative examples, the resin film serving as the protective layer was subjected to the MIT test according to JIS P 8115. Specifically, the resin film was cut into a length of 15 cm and a width of 1.5 cm to prepare a measurement sample. The measurement sample was attached to an MIT folding fatigue tester BE-202 type (manufactured by Tester Sangyo Co., Ltd.) (load 1.0 kgf, clamp R: 0.38 mm) and repeatedly bent at a test speed of 90 cpm and a bending angle of 90°, and the number of times the measurement sample was bent when it broke was taken as the test value. The results are shown in Table 1.

[0077] (2) Loss tangent tanδ of the protective layer (resin film) The loss tangent tan δ of the resin films used in the examples and comparative examples was measured under the following conditions using a dynamic viscoelasticity measuring device (manufactured by IT Keisoku Seigyo Co., Ltd.). The results are shown in Table 1. <Measurement conditions> Measurement temperature: 85℃ or 100℃ Measurement humidity: 85RH% (relative humidity) *85℃の場合のみ Mode: Tensile Frequency: 5Hz Sample width: 5mm Chuck distance: 20mm

[0078] (3) Flexibility of OLED displays The polarizing plates obtained in the examples and comparative examples were attached to a transparent polyimide film (KOLON, thickness 25 μm) with an acrylic adhesive (thickness 15 μm) as a dummy for a bendable organic EL panel. The thickness ratio of the protective layer to the thickness of the organic EL panel is shown in Table 1. Next, the obtained evaluation sample was cut into a 100 mm x 20 mm rectangular shape with the absorption axis direction of the polarizer as the long side. The cut sample was set in a no-load U-shaped stretch tester (Yuasa System Co., Ltd.'s "Small tabletop durability tester DLMD111LHA" and "U-shaped stretch test jig") so that the polarizer side was on the inside of the bend, and a bending test was performed under the following conditions. Environmental conditions: 25℃, 55%RH Test speed: 60 rpm Bending radius: R3 Number of flexes: 10,000 Thereafter, the flexibility of the organic EL display device was evaluated according to the following criteria. The results are shown in Table 1. ◯: No cracks in the polarizing plate. ×: The polarizing plate has a crack.

[0079] <<Preparation Example 1: PC Resin Film>> 81.98 parts by mass of isosorbide (ISB), 47.19 parts by mass of tricyclodecane dimethanol (TCDDM), 175.1 parts by mass of diphenyl carbonate (DPC), and 0.979 parts by mass of cesium carbonate 0.2% by mass aqueous solution as a catalyst were charged into a reaction vessel, and in a nitrogen atmosphere, the temperature of the heating vessel was heated to 150°C as the first step of the reaction, and the raw materials were dissolved (about 15 minutes) while stirring as necessary. Next, the pressure was changed from normal pressure to 13.3 kPa, and the temperature of the heating vessel was raised to 190°C in one hour, while the generated phenol was extracted outside the reaction vessel. After the entire reaction vessel was kept at 190°C for 15 minutes, the pressure in the reaction vessel was changed to 6.67 kPa, the temperature of the heating vessel was raised to 230°C in 15 minutes, and the generated phenol was extracted outside the reaction vessel as the second step. As the stirring torque of the stirrer increased, the temperature was raised to 250°C in 8 minutes, and the pressure in the reaction vessel was allowed to reach 0.200 kPa or less in order to remove the phenol that was generated. After reaching a predetermined stirring torque, the reaction was terminated, and the reaction product was extruded into water to obtain pellets of PC-based resin. The obtained PC-based resin was vacuum-dried at 100°C for 12 hours, and then a PC-based resin film with a thickness of 25 μm was produced using a film-forming device equipped with a single-screw extruder (manufactured by Toshiba Machine Co., Ltd., cylinder setting temperature: 250°C), a T-die (width 1700 mm, setting temperature: 250°C), a cast roll (setting temperature: 60°C) and a winder. The in-plane retardation Re (550) of the PC-based resin film was 3.0 nm.

[0080] <<Preparation Example 2: PC Resin Film>> A PC resin film was produced in the same manner as in Preparation Example 1, except that the thickness was changed to 45 μm. <<Preparation Example 3: PC Resin Film>> A PC resin film was produced in the same manner as in Preparation Example 1, except that the thickness was changed to 60 μm.

[0081] [Example 1] As a thermoplastic resin substrate, a long amorphous isophthalic copolymerized polyethylene terephthalate film (thickness: 100 μm) having a Tg of about 75° C. was used, and one side of the resin substrate was subjected to a corona treatment. A PVA aqueous solution (coating solution) was prepared by adding 13 parts by mass of potassium iodide to 100 parts by mass of a PVA-based resin prepared by mixing polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., product name "GOHSEFFIMER") in a 9:1 ratio. The solution was dissolved in water. The above PVA aqueous solution was applied to the corona-treated surface of a resin substrate and dried at 60° C. to form a PVA-based resin layer with a thickness of 13 μm, thereby producing a laminate. The obtained laminate was uniaxially stretched 2.4 times in the machine direction (longitudinal direction) in an oven at 130° C. (auxiliary air stretching treatment). Next, the laminate was immersed in an insolubilizing bath (a boric acid aqueous solution obtained by mixing 4 parts by mass of boric acid with 100 parts by mass of water) at a liquid temperature of 40° C. for 30 seconds (insolubilizing treatment). Next, the film was immersed in a dye bath (an aqueous iodine solution obtained by mixing iodine and potassium iodide in a weight ratio of 1:7 with 100 parts by mass of water) at a liquid temperature of 30°C for 60 seconds while adjusting the concentration so that the single transmittance (Ts) of the finally obtained polarizer would be the desired value (dyeing treatment). Next, the piece was immersed in a crosslinking bath (a boric acid aqueous solution obtained by mixing 3 parts by mass of potassium iodide and 5 parts by mass of boric acid with respect to 100 parts by mass of water) at a liquid temperature of 40° C. for 30 seconds (crosslinking treatment). Thereafter, the laminate was immersed in an aqueous boric acid solution (boric acid concentration: 4% by weight, potassium iodide concentration: 5% by weight) at a liquid temperature of 70°C and uniaxially stretched in the longitudinal direction (longitudinal direction) between rolls with different peripheral speeds to a total stretch ratio of 5.5 times (underwater stretching treatment). Thereafter, the laminate was immersed in a cleaning bath (an aqueous solution obtained by mixing 4 parts by mass of potassium iodide with 100 parts by mass of water) at a liquid temperature of 20° C. (cleaning treatment). Thereafter, the film was dried in an oven maintained at about 90° C. while being brought into contact with a SUS heated roll whose surface temperature was maintained at about 75° C. (drying shrinkage treatment). In this manner, a polarizer having a thickness of about 5 μm was formed on the resin substrate, and a laminate having a resin substrate / polarizer structure was obtained. The polarizer surface (the surface opposite to the resin substrate) of the obtained laminate and the PC resin film (first protective layer) obtained in Preparation Example 1 were bonded together using an adhesive (specifically, an active energy ray-curable adhesive), and the adhesive was cured by irradiating with ultraviolet light. Next, the resin substrate was peeled off, and the peeled surface of the resin substrate in the polarizer and the PC resin film (second protective layer) obtained in Preparation Example 1 were bonded together using an adhesive (specifically, an active energy ray-curable adhesive), and the adhesive was cured by irradiating with ultraviolet light. In this manner, a polarizing plate having a structure of first protective layer / polarizer / second protective layer was obtained.

[0082] [Example 2] A polarizing plate was obtained in the same manner as in Example 1, except that the PC resin film in Preparation Example 1 was changed to a COP resin film having a thickness of 50 μm (manufactured by Zeon Corporation, product number ZF16).

[0083] [Example 3] A polarizing plate was obtained in the same manner as in Example 1, except that the PC resin film in Preparation Example 1 was changed to an acrylic resin film having a thickness of 25 μm (manufactured by Kaneka Corporation, product name "HTX-Z").

[0084] [Example 4] A polarizing plate was obtained in the same manner as in Example 1, except that the PC resin film in Preparation Example 1 was changed to a PET film having a thickness of 40 μm (manufactured by Toray Industries, Inc., product number "50U48").

[0085] [Example 5] A polarizing plate was obtained in the same manner as in Example 1, except that the PC resin film of Preparation Example 1 was changed to the PC resin film of Preparation Example 2.

[0086] [Comparative Example 1] A polarizing plate was obtained in the same manner as in Example 1, except that the PC resin film of Preparation Example 1 was changed to the PC resin film of Preparation Example 3.

[0087] [Table 1]

[0088] [evaluation] As is clear from Table 1, when the protective layer is bent 200 times or more in the MIT test, by applying a polarizing plate having the protective layer to an organic EL display device, it is possible to impart excellent flexibility to the organic EL display device. [Industrial Applicability]

[0089] The polarizing plate of the present invention can be applied to image displays, and can be suitably used in particular in bendable or foldable organic EL display devices. [Explanation of symbols]

[0090] 1 protective layer 2 Polarizer 100 Polarizing Plate 200 Image display device

Claims

1. A polarizer; a protective layer disposed on at least one side of the polarizer; The polarizing plate, wherein the protective layer is bent 200 times or more in an MIT test.

2. An image display device comprising: the polarizing plate according to claim 1; and a bendable image display panel, in this order.

3. 3. The image display device according to claim 2, wherein a ratio of a thickness of said protective layer to a thickness of said image display panel is 1 to 2.

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